The present invention relates to pressure differential operated boosters for use in automotive brake systems.
A conventional tandem servo booster typically includes a housing, a partition secured within the housing to divide the interior of the housing into front and rear chambers, and two diaphragms located on opposite sides of the partition and adapted to divide the interior of the front and rear chambers into front and rear constant and variable pressure chambers, respectively (see FIG. 5). The it partition and diaphragms are secured to a valve body. An H output rod is connected to the valve body through an elastomeric reaction disk. An input rod is coaxial with the output rod and is connected to a plunger which is slidably received in the valve body. The front and rear constant pressure chambers are permanently communicated with a vacuum source. Normally, the plunger is urged into its retracted position so as to hold all the four chambers in communication with the vacuum source. When the brake pedal is depressed, an input force is applied to the input rod to activate the plunger. The plunger is then unseated from a valve seat to interrupt vacuum communication between the constant pressure chambers and the variable pressure chambers and in turn, cause ambient air to enter the front and rear variable chambers. With the air in the variable pressure chambers, a pressure differential is developed across the front and rear diaphragms. This pressure differential acts on the diaphragms so as to develop a force which is carried into the valve body for distribution into the output rod. Except for the initial stage of braking, this output force linearly increases as the input force increases (see the line F in FIG. 6). It is, thus, necessary to heavily depress the brake pedal in the event that a larger braking force is required at the time of X emergency.
It is, therefore, an object of the present invention to provide a pressure differential operated brake booster which can readily produce a greater degree of braking force without the need to increase the force required to depress the brake pedal.
It is another object of the present invention to provide a pressure differential operated brake booster which enhances a "jump-in" effect at the time of emergency.
It is a further object of the present invention to provide a pressure differential operated brake booster which allows for ready and safe assembly of adjusting means within a valve body.